Method of and machine for grinding gears



July 4, 1939. E. WILDHABER METHOD OF AND MACHINE FOR GRINDING GEARS Filed Jan. 6, 195'! 5 Sheets-Sheet 1 T 27 w l/ 25 I I 214/ 2! T 6 1 22 Z1 I Inwcntor Cum-um July 4, 1939. E. W|LDHABER 2,164,978

METHOD OF AND MACHINE FOR GRINDING GEARS Filed Jan. 6, 1937 5 Sheets-Sheet 2 CQWZAQ/E NM Gttsrncn July 4, 1939. E. WILDHABER 2,164,978

METHOD OF AND MACHINE FOR GRINDING GEARS Filed Jan. 6, 1937 5 Sheets-Sheet 3 Enventor Ytforneg July 4, 1939. E. WILDHABER METHOD OF AND MACHINE FOR GRINDING GEARS Filed Jan. 6, 1937 5 Sheets-Sheet 4 6/ mung July 4, 1939. E. WILDHABER METHOD OF AND MACHINE FOR GRINDING Filed Jan. 6, 1957 GEARS 5 Sheets-Sheet 5 x Y 7 Ema 195 m @2656 Z/LZ Smacntor (Ittomeg V Patented July 4, 1939 UNITED "STATES METHOD. OF AND MACHINE FOR GRINDING GEARS Ernest Wildhaber, Irondequolt, N. Y., assignor to Gleason Works, Rochester, 'N. Y., a corporation of New York Application January 6, 1931, Serial No. 119,287

. 12 Claims. The present invention relates to the grinding of straight toothed gears both spur and bevel,

and particularly to the grinding'of such gears in a generating operation with a plane-sided wheel. v

Heretofore two principal methods of grinding straight toothed gears in a generating process have been used. In one of these methods, a plane-sided grinding wheel of relativelylarge diameter is employed and the wheel is fixed against movement longitudinally of the teeth of the gear and the tooth surfaces of the gear are ground by simply rotating the wheel on its axis while effecting the relative generating roll between the wheel and the gear. In the other method, the grinding wheel, which may be either a plane-sided or a conical wheel, is moved relatively longitudinally along a tooth of the gear as the wheel is rotated on its axis and the wheel and gear are rolled relative to one another. The first method is quite fast but is restricted to'use in the grinding of gears of narrow face-width.

The second method is relatively slow because to grind the full tooth surfaces of a tooth, the grinding wheel must be rolled with the gear not merely in one position, as in the first method, but continuously back and fortl'ras the wheel moves relaground.

tively lengthwise of the tooth surface being One main object of the present invention is to provide a method of grinding straight toothed gears which is capable of handling gears of greater face-width than heretofore possible but which will not require any feed motion along the length of a tooth of the gear.-

Another object of the invention is to provide a method of generating straight toothed gears which will permit of employment of a stronger type of grinding wheel than has heretofore been possible in the generating methods heretofore practiced.

A further object of the invention is to provide a method of grinding straight toothed gears in which a pair of grinding wheels may be employed V for grinding opposite sides of the teeth of, a gear simultaneously and the wheels used will have a longer life and a larger usable amount of abrasive stock than wheels usable with the processes heretofore employed. Still another object of the vide a method of grinding straight toothed gears in which a pair of grinding .wheels' may be employed andthe wheels may be 'setto a constant angle and adjusted jointly to compensate for wear and to permit dressing.

invention is to pro- I A still further object of the invention is to provide amethod for grinding straight toothed gears which will require a minimum amount of generating roll and, in fact, no more roll for two wheels than would be required if a single wheel only were used in the grinding process.

Other objects of the invention will appear hereinafter from thespecification and from the recital of the appended claims.

In the drawings:'

Fig. 1 is a diagrammatic view showing the rela-- tive positions of a grindingwheel'and gear at different points in the roll in the process of grinding a gear by the method of the present inven-' tion and showing, also, by way of comparison,

the corresponding poistions of wheel and gear in I the grinding methods heretofore employedr Fig. 2 is a diagrammatic view showing how a pair of grinding wheels, whose pressure angles are greater than the pressure angles of the tooth surfaces to be ground, may be employed in grinding gears according to one modification of the present invention;

Figs. 3 and 4 are diagrammatic views illustrating, respectively, positions of the grinding wheels shown in Fig. 2, at opposite ends of the roll in the generation of a gear;

Figs. 5 and 6 are diagrammatic views showing how the amount of generating roll may be kept at a minimum on gears of different numbers of wheel assumes in the grinding of gears according to the present invention;

Fig. 8 is a longitudinal .view, with parts broken I away and shown in section, of a grinding machine built according to one embodiment of this invention for grinding straight toothed bevel gears;v

- Fig. 9 is a view, showing a detail of the drive to the work spindle;

Figs. 10 andll are views showing details of the drive of the wheel carriers, the view of 'Fig. 11 being taken at right angles to the view of Fig. 10 and from below; g

Figs. 12 and '13 are views taken at right angles to one another and showing a detail of the drive tonne of the grinding wheels of the machine; and

Fig. 14is a drive diagram of the machine.

The present invention deals directly withthe grinding of gears with a plane-sided wheel where the wheel has no movement longitudinally of the gear teeth. Heretoiore, in grinding the involute or substantially involute tooth sides of a straight toothed gear with such a wheel, the grinding wheel and the gear have simply been rolled together as though the gear were meshing with a rack or crown gear represented by the wheel. In the present method, the generating roll is retained. but in addition, the grinding wheel is f depthwise into the gear being groimd, as it withthegear,sothatat oneorboth endsof roll it may engm with the teeth of the gear at a greater depth than would be possible in a rolling motion and hence may grind the sides of thegearteethtoagreaterdepththanhasheretofore been possible.

The old and new methods of grinding are illustrated for comparison in Fig. 1.

In this figure, It denotes the gear to be ground and 2| the grinding wheel. The active grinding surface of the wheel is denoted at 22 and lies in a plane perpendicular to the axis 23 of the wheel.

Root, pitch and top surfaces of the gear are denoted at 25, 20 and 21, respectively and the root and pitch planes of the gear are denoted at 28 and 2!, respectively. The pitch plane is the common plane tangent to the pitch surfaces of the gear being ground and of the basic gear .represented by the grinding wheel. In spur and bevel gears, the pitch plane is perpendicular to the plane containing the axes of the gear being ground and of the basic generating gear represented by the grinding wheel.

In Fig. 1, the grinding wheel is shown as posi-' tioned to grind the side surfaces II of the gear teeth SI and the wheel is adjusted angularly so that its active side surface 22 is inclined to the pitch plane 29 of the gear at an angle equal to the pressure angle of the tooth surfaces ll to be ground.

In the prior-art method of grinding, the pitch surface 26 of the gear is rolled on the pitch plane of the rack or crown gear represented by the wheel. This plane coincides with the plane 2!.

If we imagine that in such prior process, the generating roll is divided, that is that the gear turns on its axis which remains stationary and that the wheel 2| moves in the direction of the pitch plane 2!, then the-outside or tip point of the wheel will move on the line ll and at opposite ends of the roll, the wheel will assume the positions denoted at 2i and II".

In the position shown in dotted lines at Ii, the wheel will grind and completelyform the root portion or flank of the tooth sides I. in the middle section of the gear. At the ends of the tooth, however, the wheel does not reach quite so deep into the tooth space because it is circular (see Fig. '7) and at a certain distance away from the center of the tooth face, stock will be left on the tooth surfaces which will interfere with the mesh between the gear and its mate. The distance at which interfering stock may be left on the tooth sides determines the maximum facewidth, of the gears which may be ground by the previous process without motion of the wheel longitudinally of' the tooth'surfaces of the gear. The limit face width equals twice said distance.

In the process of. the present invention, an additional motion is provided between the work and the grinding wheel in the plane of the active surface of the grinding wheel during the rolling motion. The grinding wheel is fed deeper into arses-rs wheel is moved deeper into the tooth space 82 of the gear as the wheel rolls from the central position 2! to the left and will have the position Ila instead of the position ii. The grinding wheel will then reach beyond the 'root plane II of the gear at this end of the roll and finish the lower flank of the tooth side 30 more completely than was possible in the previous process. Hence gears of increased face-width may be ground by the process of the presentv invention without longitudinal movement of the grinding wheel. The grinding wheel may be advanced in the direction of its active surface until it nearly touches the root surface 25 of the gear being ground.

The described feed motion in the plane of the grinding wheel is timed with the generating roll. It does not need to be very accurately timed to the roll, however, nor does the motion itself require particular accuracy inasmuch as it does not affect the shape of the tooth surfaces but only the extent of the finished portion of these surfaces.

The same mechanism which is employed to produce the described motion in the plane of the active surface of the grinding wheel may also be used to effect withdrawal of the wheel from engagement with the gear after a tooth surface has been ground to permit of indexing the gear.

This is shown clearly in Fig. 7, where two positions of the wheel, at full depth and in withdrawn position. are shown in full and dotted lines, respectively. Here the feed of the wheel into depth is assumed to take place about an axis 35 and the center of the wheel in the two positions of its movement is denoted at 88 and 36', respectively.

In the rolling movement of the wheel 2| to the right (Fig. 1) in the grinding of the tooth surfaces ll of the gear 20, it is not-necessary to employ a feed motion in the direction of the plane surface of the wheel since in this direction of roll. the grinding wheel is operating upon the portion of the tooth surface Ill adjacent the tip of the tooth. It is desirable, however, to employ this motion during roll of the wheel to the right, also, forby imparting this feed motion to the wheel in this direction of the roll, also, wear of the grinding wheel is distributed over an increased length of the wheel profile. Hence it is desirable to move the wheel inwardly from the position II to a positionsuch as indicated in dotted linu at lib as the wheel moves to the right. Thus at the right end of the roll, the wheel also, will extend deeper into the tooth space of the gear than at the position II".

The advantage of using the feed motion in the plane of the active surface of the grinding wheel is increased where the gear is ground conjugate to a rack or crown gear whose tooth surfaces have a pressure angle greater than the pressure angle of the gear to be ground. This is illustrated in- F188. 2. v3 and 4.

Here are shown two grinding wheels ill and il for grinding opposite side surfaces 42 and. it, respectively, of the teeth ll of the gear 45.

The wheels have active surfaces .46 and 41, respectively, which are plane surfaces perpendicular to the axes of the wheels and they are adjusted angularly so that their plane side surfaces are inclined to the pitch surface it of the gear at an angle greater than the pressure angle of the tooth surfaces to be ground.

To'attain the proper tooth profiles and pressureangles on the gear l5, then the gear is rolled noton its pitch circle 40, but on a circle 50 which is larger than its pitch circle and which rolls on between the the line Ill, that represents the pitch plane of the basic rack or crown gear, represented by the wheels during the generatingoperation. 58 and 54 are lines of action between the and the grinding wheels during generation of the tooth I5 isa line of action betweenproiiles, whereas the gear and its mate when the pair are in mesh.

Figs. 3 and 4 show, respectively, positions of the gear and wheels'at opposite ends of the generating roll.

With prior methods ofgrinding, the tip surfaces of the grinding wheels remain'outside, that tions indicated at 40 and 4|,respectively, at the flank of the "sides 42 of the teeth of the gear-and this stock will prevent correctmesh when. the

gear isrun with its mate. Hence the face-width of the gear which may be ground is definitely limited.

With the method of the present invention,

however, the grinding wheel 40 is fed in depthwise as it rolls with thegear and will occupy the position indicated at 40a at the leftend of the rolllthrough displacement of the wheel in its plane 46 and the'tooth surface will be finished to a greater depth andhenceto a greater width. Correspondingly in the rightward roll of the wheel, the wheel II will be moved inwardly below the .tangent Wand will occupy the position de-..

noted at 4Ib in' Fig. 4 so that-the opposite sides 43 of the gear teeth-may be properly finished. -It is even possible with the present invention to undergrind the tooth flanks with the flat sides of the grinding wheel, if so desired, by further extending the roll.

One advantage obtained by the use of'an .increased pressure anglefor generation is the .fact

that the grinding wheels or .wheel may be adjusted ior dressing in a direction perpendicular to the direction of roll whereas, otherwise, as indicated in Fig. 1, the grinding wheel must be adjusted in an oblique direction, as denoted at El, unless a much weaker form of grinding wheel .is used.

Another advantage of the use of an increased pressure angle for generation is that the wheels can be kept more readily clear of one another and hence stronger and longer-lived wheels can be employed. Preferably the grinding wheels are set to a constant angle and are jointly adjusted for dressing.

On gears with moderate numbers of teeth, such as shown in'Figs. 1 and 2, the provision of the increased pressure angle helps to reduce the total rollrequired to fully 'generaterboth sides of .the

gear teeth. In the generation of -a gear such as I shown in Fig. 2 with a pair of plane sided wheels, the total roll required is not any larger for the two wheels than it would be for a single wheel.

Figs. 5 and6show how the amount ofroll may.

be kept small even with gears having larger numbers of teeth,without. altering the relative angular position'jof the two wheels. In Flg. 5, the two grinding wheels and 86 are spaced two tooth spaces apart in the grinding of the; opposite sides 68 and 610i the teeth of thegear 68. In Fig. 6, the grinding wheels I0 and II are spaced three tooth spaces apart-in the grinding of the opposite sides .of the teeth oi the gear I3 I which has a greater number of teeth than either the gear 68 or the gear 45. In all of the ,cases illustrated in Figs. 2, 5 and 6, however, the angle u designates the base or chine, G is the bevel gear blank to be ground'and W and W are the grinding wheels.

lane sides or thegrinding, wheels remains constant, thatis, theangle between. the sides 481 and 41 in Fig. 2 is equal to the angle be tween the sides .l4-and "in Fig. 5 and the sides I8 and I1 in Fig. 8; Further, with the arrangements shown in Figs. 5 and 6, it is possible to keep the roll as small as it would be where a single wheel *is used In Figs.--8.to more or less diagrammatically one form of machine for grinding straight bevel gears according to thisinvention.

frame ofthe ma The gear-to be ground is secured able mannerto a work spindle 81 which. is Journaled in a work head 82. The work head 82 is formed with a circular-shaped foot portion 88 which seats on theupper face. of-a circularlyfshape: rest 84 which forms a part of asliding base-5.

in any" suit- 14 inclusive, rhave illustrated The 85 is laterally-adjustable upon asupporting bracket 81 which is integral with the face-plate or cradle 88..

' The foot 88 of the work head 'andthe sup porting rest 84 of the base 85} have oppositely beveled peripheral surfaces. The work head is angularly adjustable on the rest 84 to position the work-spindle in accordance-with the cone.

angle of the gear to be ground and the work head may be secured to the supporting base in any position of its angular adjustment by the clamping ring 88-. This'ring is of the split type and is formed'internally with a generally V- shaped groove, the opposite sides of which engage with the beveled surfaces of the foot portion is shown swung out of operative position in Fig. 8. Adjustment of the slide 85 upon the bracket 81 permits of adjustment of the work spindle in accordance with .the cone distance of the gear to be ground. The slide 85 may be secured to the bracket 81 in any' adjusted position by T-bolts (not shown) which engage in the slots 90 and 9|.

The cradle 881s journaled ona column or upright and is secured in position on the column by' the circular gib '96 and the screws 91. The column is slidably mounted upon the base 80 of the machine and is reciprocable ther'eon to move the gear into and out-of engagement with the grinding wheel, as will'be described in more detail hereinafter.

There is a spur gear segment-I 00 secured to the cradle 88 byv screws IN. This segment meshes with a rack I02 which isreciprocably mounted upon the column 95 and which is held in position 83 and of the supporting rest 84. The work head on the column by the straps I03 and I04 and the screws I05 and I08. The rack I02 is reciprocated by means which will .be described more particularly hereinafter to i to the cradle. e

Fixedly secured to the column 85 in a position coaxial of the cradle is abevel gear I01. A, bevel pinion I08 mesheswiththis bevel gear. This 1 pinion is secured to a shaft I09 which is journaled in a bracket-like extension I I0 of the cradle 88. I

There is a spur gear III secured to the outer t end of this shaft and this spur gear meshes with a spur. gear-H2 which is mounted upon a stud impart an oscillating motion I is that is secured .in a quadrant I I4. The quadrant H4 is mounted upon the bracket IIOso: as e e to be adjustable angularly-about the axis of the shaft I09. Thereis-a second spur gear '5,

moimudupcnthestudlll'andthlsgearmeshes with a spur gear III which is securedto the shaft Ill.

This shaft is journaled in'a sleeve Iii-which is secured in any suitable manner to the work head I; There is a bevel pinion III keyed to the lowerendofthisshaftandthlspinionmesheswith a bevel gear III which is keyed to the work spindle II.

V Through thegearingdescrlbed, itwillbeseen that when the rack I" is reciprocated. an oscillatory movement will be imparted to the cradle II and simultaneously the work spindle OI willbe rotated in one direction or the other upon its axis.

Thus the generating motion is imparted to the Eachofthewheel-carrlers Illlsjournaledina bearing I" (Hg. 12) and each wheel carrier I" has a trunnion m secured to it byscrews III that is journaled in a bearing III which is of the split type and is closed by an end-cap I40.

Thebearlngs Ifland laareintegralwlthan up i ht or column I which is integral with or .securedtothebaseslofthemachine. Thus,the

m and m.

grinding wheel carriers are rotatably mounted upon the column I for oscillation to effect the depthwisemovement of thewheels' as will now be dmcribed. Mounted at anyeonvenient point upon the machine is a main drive motor Ill (Hg-14).

Secured to one end of the shaft". (Fig. 14, 10 and 11) is a crank I'll which drives a rod I'll .through an adjustable pin I'll and the block "8.

The block engages in a longitudinal slot I'll formed in a member In which is fastened in any suitable manner to the rod III.

Thereisarackmember I'll securedtotherod I'll and this rack member meshes with pinion I'l'l which is fastenedfo a cured'to the upper end I". Thegearlll'formedwith or projection I which is mite a and is secured to a.

and fastened to the other end bevel. gear Ill.

housing are bevel gears I, III and I82. bevel gear I is secured to a shaft I. The bevel gear III is a planetary gear and is mounted upon a shaft I which is journaled at'both ends in the housing I". The bevel gear I" is secured to a shaft III which projects from one end end of the housing and which is keyed to a bevel gear Ill (Figs/i4 8). This bevel gear Ill mesheswithabevelgearsegmentfllwhichis boltedtoanarmili thatlsintegralwith the wheel carrier III for the wheel W.

The bevel gear Ill meshes with a bevel pinion III that is secured to a stud shaft 208. This stud shaft is lournaled in the dlflerential housing Ill. and is keyed to a face-clutch member zss which has clutch teeth on its inside face that are adapted to be engaged with clutch teeth formed on the opposed face of the diflerential housing.

The pinion It! meshes with a bevel gear III which is secured to a shaft 2".

Keyed to the shaft III is'a cam III that engages a roller Iii carried by an arm 2". The arm I" is secured to a differential housing 2I8. Mounted in this housing are the bevel gears 220. iii and 222. The bevel gear 220 is secured to a shaft 224, one end of which is journaled in the differential housing. The bevel gear MI is a,

planetary gear and is secured to a shaft m. which is journaled at both ends in the housing Ill. The bevel gear 122 is secured to a shaft III, which is journaled at one end in the housing. There Is a bevel gear as keyed to the shaft Ill. This bevel gear meshes with a bevel gear segment Ill which is bolted to an arm III that is integral with the carrier is! for the wheel W.

Through the mechanism above described, it will beseen that the cams I83 and III are rotated first in one direction and then in the other. As these cams oscillate, they impart an oscillatory movement-to the segments 200 and 280, respectively, through thediiferentlal housings Ill and ill, respectively, and the gearing connecting these housings with the segments. Thus the carriers I" are oscillated imparting oscillating movement to the wheels W and W in the planes of the active side surfaces of these wheels. Thuathe'dulred depthwise movement may, be hnparted to the wheels toeffect grinding ofthetooth surfaces of a gearto' a greater Mdepthaccordingtothedescribed basic principle of this invention.

The cams Ill and III are similar in conformation and are of opposite hand since one grinding wheel "is fed depthwise in the movement to ward one end of the roll and the other wheel is fed depthwise in the movement toward the opposite end of theroll, aswlll clearly be seen from Figs. 8 and 4. 'Ihe cams I and III impart the samemovement when turned in Opposite directions. Thecams Ill and II! canbe adjusted angularly relative to one another by disengaging the clutch member 208 and rotating the shaft '2 while the clutch is'open. The clutch member isheld in engaged position by the nut 23! which threads ontothe outer end of the shaft 106. Toeflect indexing of the work after grinding of a pair of tooth surfaces, the grinding wheel carriers are swung about their respective axes to withdraw the wheels from the gear and then the index mechanism is actuated. After indexing is complete, the carriers are swung back to return the wheels to operative position. The mechanism for effecting the withdrawal and return movements of the wheels will now be described.

Secured to the shaft I'll is a spur pinion 240 (Figs. 14, 10 and 11). This pinion meshes with a spur gear "I which is keyed to a shaft 242. Keyed to the shaft 2411s a.cam 2. This cam gnagages a roller 2 which is carried by an arm I justments are made,- the machine may be started.

When the gear is in operative position, the gena gear meshes with a bevel gear 249 which is keyed tened to this shaft is a bevelgear m. This bevel to the shaft m. The shaft m'ls aligned va i y with the shaft 224 and the two'shafts are connected together to rotate together-by acoupling 249'(Flgs.'8 and i4). Throughthe mechanism the withdrawal and return movements of'the I 7 1 'wheels are effected.

just'described and'the-diiferentlals Ill and 219,

The generating motion is derived from the shaft 250 through the bevel-gears Sand 2, the shaft 252, the bevelgears 253 and 254,, the shaft 255, the bevel gears and 251, the shaft 268, the crank 290,- crank-pln' 29L rod 263, rack I02 and spur gear segment I99.

The gear being ground isthus rolled back and forth under the oscillating grinding wheels.

In'the machine illustrated, it is intended to roll the 'work back and forth-severaltimes over the grinding'wheels before withdrawing the wheels and indexing; For this reason, thegearrotate several times mg 240-24lis selected sothat the crank I19 for a single revolution of the vcam 243. v w

, To eflectjgradual removal. of stock and to" avoid repeated grindings in the same positions on the gearon successive roll -movements, the

gear is fed slowly into-the wheels during the rolling-movements.

The feed movement is imparted to the column 95. This movement is derived from the shaft I51, the drive being through the worm 210 and worm wheel 2', shaft 212, bevel gears 213 and 214, shaft 215, cam 216, roller 211 which engages' said cam, shaft 218, spur pinion 219 (Figs. 8' and 14), and rack 28!). The roller 211 is carried by an arm 282 which is keyed or otherwise "secured to the shaft 218.

Thegrinding wheels may be driven in any suitable manner. "As shown in the "drawings,

both wheels are driven from thesame motor 285 (Fig'.- 13) which is mounted in any convenient location upon the machine. This motor is connected by a belt 286 (Fig. 13) and a pair of pul-' leys 281 and 288 with a shaft 289. This shaftdrlvesthe shaft 290 through a pair of mitre gears 29! and 292. The shaft 2st drives the spindle ml of the grinding wheel w' through the belting 294 and pulleys 2 and 296. An idler 291 is provided totake up slack in the belting.

. The othergrindi'ngwheel W- is driven from the shaft 290 through the mitre gears 298 and 299. The mitre, gear 299 issecured to a shaft 290 which extends parallel to'the wheel spindle I39 and like the. shaft 299 carries a'pulley which drives the wheel spindle I30 through a drive corresponding to the pulley drive'described for the wheel spindle" Hi. The mountings of theshaft 299 and wheel carrier are shown'moreor less diagrammatically in Fig. 13 for the sake of clearness in illustration.

The operationof the illustrated machine will be apparent from theabove description but may briefly be summed up'here. After the various aderating roll starts and the grinding wheels rotate .on their axes while the gear is rolled over-them. During each rolling movement, thewheel carrlers are oscillated toefiect the depthwise move- 'ment'. During relative movement of gear and wheels towardone end of the roll, the wheel w is moved into extra depth and during relative movement toward the other end of theiroll, the

u I an ora The arm m'le secured to 11min. l 'ass '5. wheel w" is moved me extra depth. The gear is rolled back andjforthover the wheels several times before it is indexed and during theserolling movements, the gear is-gradually fed. into depth. When'thetooth surfaces have been fully ground, the wheels-are'swung away from the gear by movement of thewheel. carriers and when the wheels have been fully withdrawn, the gear is indexed At this time also, the column 95. is withdrawn the amount of the'previous feed movement. When the indexing operation is completed, the cycle begins anew, the wheels being re-- turned into engagement with the gear and the -r'oll.and feed. movementsbeginningagain. The

alternate grinding and indexing proceeds until all of the teeth. of the gear have been finish groun'd. Then the machine may be stopped by automatic means such as' usually employed on machines for producing gears and the completed .gear may be 'removedand a new gear chucked.

' No dressing mechanism has-been shown upon the machine, but the dressing mechanism may be of any suitable type. If the wheels are adjusted and. the roll gearing is so selected that the wheels H represent a basic gear having teeth, of larger pressure angle than the tooth surfaces of the gear faces of the wheels; Likewise, wear of the wheels umn 95 to feed the gear intothe wheels. The angle'between the wheel spindles may be kept constant and gears of different tooth numbers may be ground with the wheels spaced different distances apart, as shown in Figs.- 5 and 6; A-

suitable adjustment to-- permit of spacing the wheels for this purpose may be provided, but has not been shown upon the machine illustrated in the drawings. I I a In the drawlngathe inventionhas been illustrated in connection'with a machine forgrinding straight bevel gears-conjugate to a crown gear having plane tooth sides. It will be understood, however, that the invention is also applicable to the grinding of straight bevel gears conjugate-to a non-generated of Formate.gear.

. applied to the essential features hereinbefore set forth and as fall within the scope ofthe inventionor the limits of the appended claims.

Having thus described my invention, vwhat I claim is: I I

l. The method of grinding a gear which consists in employing a grinding wheel-which has a plane active face extending at right angles to the axis of the wheel, positioning said wheelv in en-' gagement with the gear so that the axis of the wheel is inclined to the pitch plane of the-gear,

and rotating the wheel on its axis and producing a relative rolling movement between thegearand -t o:begr ound, the dressing mechanism may bead- Ivanced relatively toward the wheels along a line bisecting the angle between the plane side sur- 4 30 can be compensated for by movement of the-colthe wheel to cause the plane active face of the wheel to grind a side surface of a tooth of the 'gear, while effecting a. relative depthwise feed movement between the wheel and gear intime with the relative'rolling movement so. that the.

E E E rolling movement, in full depth position, the willextendinsidetherootplaneoithe inemploying agrinding wheel which hssa active lace extending at right anglesto its ,ensasinssaidwheelwiththegearsothat so that at one end 0! the rolling movement, in full depth position, the wheel will extend inside the root plane 01' the gear.

4. The method of grinding a gear which consists in employing a pair of plane-sided grinding wheels, engaging the wheels with the gear with their axes inclined to the pitch plane of the gear and angularly disposed to one another and so thatthe plane sides 01' the wheels engage opposite sides of spaced teeth oi the gear. rotating the wheels on their respective axes and, while producing a relative rolling,movement between the wheels and gear, ieeding the wheels independently of one another depthwise into the gear in the directions of the plane sides of the wheels. said teed movements being so timed to the rolling motion that at one end 0! the rolling motion, one

of the wheels extends inside the root plane 0! 3 ducing a relative rolling movement between the wheel and work, and means for feeding the wheel depthwise into the work simultaneously and in time with said rolling movement'in the direction oitheplanesideotthewheelsothatatoneend 'oi the rolling movement, in full depth position,

the wheel will extend inside the root plane of the se r- 6. In a machine for grinding gears, a work support, a grinding wheel having aplane activeiace perpendicular to its axis, a support for said wheel mounted to be swingable about an axis perpendicular to the plane side or the wheel,

' means for positioning the'wheel so that its axis is inclined at other'than a right angle to the pitch plane of the gear, means for rotating the wheel on its axis, means for producing a relative rolling movement between the wheel and gear, and

, e depth at one end therollingmovementso that atoneendoi The method of producing a gear which conmeans for simultaneously eilecting swinging movement of the wheel support in time with the rolling movement to eiIect a relative ieed movement between the wheel and sear in the direction oi tooth depth so that at one end of the rolling movement, in full depth position, the wheel will extendinside the root plane or the gear.

'LInsmachineior'grinding gearaawork .side the root plane of the gear and at the other end of the rolling movement, the other wheel will extend inside said plane.

8. In a machine tor grinding gears, a work support, a pair or grinding wheels having plane active laces engageable, respectively, with opposite sides oi spaced teeth 0! a gear with their axes angularly disposed to one another, means ior rotating the wheels on th'eiraxes, means for pro-' ducing a relative rolling movement between the wheels and gear, means for automatically eflecting relative depthwise teed movements between the wheels and gear in the direction of the respective plane side surfaces of the wheels as the gear and wheels roll together, means for periodically withdrawing said wheels, and means or indexing the gear during the periods of withdrawal.

9. In amschine for grinding gears,'a work support, a pair of grinding wheels having plane active i'aces engageable, respectively, with opposite sides of spaced teeth ot a gear with their axes angulariy disposed to one another, supports for said wheels which are oscillatable, respectively, about axes parallel to the wheel axes, respectively, means tor rotating the wheels on their axes, means for producing a relative rolling movement between the wheels and gear, and means for independently moving the wheel supports about their respective axes as the gear and wheels roll together to produce relative depthwise feed of the wheels into the gear.

10. In a machine for grinding gears, a work support, a pair of grinding wheels having plane active lacu engageable, respectively, with opposite sides of spaced teeth of a gear with their axes angularly disposed to one another, means tor rotating the wheels on their respective axes, means tor producing relative rolling movements between the wheels and gear, means for eiIecting depthwise teed movement of each oi the wheels into the gear in the direction of the plane side or the wheel during said rolling movements and in time therewith so that the two wheels grind, respectiveh, at opposite ends of each rolling movement to a greater depth than either grinds at the center of the rolling movement and so that in full depth position, the twowhe'els will extend. respectively, at oppositeends oi the rolling movement inside the root plane oi' the gear, means for relatively feeding the gear depthwise into the wheels on successive rolling movements until Iull depth position is reached and means for then relatively withdrawing the wheels from en- 16 gagement with the gear to permit indexing the gear.

11. In a machine for grinding gears, a work support, a pair of grinding wheels having plane active faces engageable, respectively, with opposite sides of spaced teeth of a gear with their axes angulariy disposed to one another, supports for said wheels which are oscillatable, respectively, about axes parallel to the wheel axes, means for rotating the wheels, means for producing relative rolling movements between the wheels and gear, means for oscillating said wheel supports independently of one another during the roll, means for oscillating said supports together to move the wheels into and out of operative position and means for indexing the work when the wheels are out of operative position.

12. In a machine for grinding gears, a work support, a pair of grinding wheels having plane active faces engageable, respectively, with opposite sides of spaced teeth of a gear with their axes angularly disposed to one another, supports for said wheels which are oscillatable, respective ly, about axes parallel to the wheel axes, means for rotating the wheels, means for producing relative rolling movements between the wheels and gear, means for oscillating said wheel supports independently of one another during the roll, means for oscillating said supports together to move the wheels into and out of operative position, said last-named means being so timed to the rolling movement that a plurality of rolling movements take place while the wheels remain in operative position and means for indexing the work when the wheels are out of operative position.

ERNEST WILDHABER. 

